Field of the Invention
The present disclosure relates to methods and apparatus for automated inspection and review of manufactured substrates, such as semiconductor wafers, using energy-dispersive x-ray spectroscopy.
Description of the Background Art
In a conventional scanning electron microscope (SEM) based inspection instrument, a manufactured substrate (such as a silicon wafer or a reticle) is scanned with a focused beam of electrons which results in the emission of secondary electrons from the substrate surface. The emitted electrons are detected, and the detection data is typically converted into images of the surface of the specimen. These images are then analyzed numerically to detect abnormalities (referred to as defects) in the manufactured substrate. The detected defects may be subsequently reviewed by further imaging.
The detected defects may also be classified, either manually or automatically, into different classes or categories. The classification of a defect may be used to determine its cause such that appropriate adjustments may be made in the manufacturing process so as to improve its yield.
In addition to producing secondary electrons, an electron beam striking a sample in an SEM also produces x-rays that are characteristic of the material of the sample. In energy-dispersive x-ray (EDX) spectroscopy, a solid state detector is positioned relatively close to the sample to collect x-rays emanating from the sample due to impingement by the electron beam. The detector receives and detects x-rays of different energies so as to obtain an energy spectrum of the detected x-rays. The energy spectrum provides information as to the elemental composition of the material being irradiated with electrons.